1. Field of the Invention
The present invention generally relates to the improvement of a lapping or polishing (hereinafter referred to as lapping) apparatus for lapping an ultra-precisely machined part (or component), a lapping jig for use in this apparatus and a workpiece mounting member which is used by being attached to this lapping jig.
2. Description of the Related Art
Hitherto, ultra-precisely machined parts, such as a magnetic head, have been required to have a finely machined surface, on which very few scratches are formed, in a final finishing step of putting a finishing touch to a surface of the magnetic head (an air bearing surface), which faces a medium. Thus, the air bearing surface is finally lapped by means of a lapping apparatus, which is designated as a lapping machine, by using industrial diamond abrasives, whose particle diameter is close to that of smallest industrially producible particles (namely, is not more than 1 .mu.m), as polishing powder (or abrasive grains). Further, especially, in the case of producing a magneto-resistance effect type head (namely, MR head) to be used as a magnetic head for a hard disk device, the productivity of the head is enhanced by giving finishing touches to the heads, which are aligned like bars, in such a manner that the height of (MR) elements is established with accuracy of better than .+-.0.2 .mu.m.
In the step of lapping such parts, there are the following demands:
(a) Stabilizing the height of MR element accurate. PA1 (b) Stabilization of the machining quality at a level at which no scratches are formed on the surface of a workpiece. PA1 (c) Increase in the working efficiency (namely, a reduction in the length of a preparation (or set-up) time other than a working time). PA1 (1) If there are slight unflatnesses, i.e., projections and depressions, formed in the radial direction on the top surface of the lapping plate, parts of the surface of the bar may be scraped by these projections and depressions with the result that irregularities may be formed on the surface of the bar. This problem is liable to occur, especially, when stopping the lapping. Further, the top surface of the lapping plate should be ultra-precisely made flat so as to enhance the flatness of the bar to be lapped. Thus, the conventional lapping apparatus has encountered the problem that the cost thereof, especially, the cost of a flattening mechanism (or facing apparatus) increases. PA1 (2) Because the lapping jig is of the swinging type, a moment is applied to an end face of the bar when the swinging direction is changed after the bar moves to the innermost or outermost periphery of the lapping plate. Consequently, the end face of the bar or the surface of the lapping plate is apt to be damaged.
Generally, after being made on a wafer, together with terminals and a recording head portion by utilizing thin film technology, MR heads are cut and formed into a plurality of bars. Then, each of such bars is turned into a head by being machined and shaped into a slider after being lapped by a lapping apparatus. This head is mounted to a tip end portion of an arm of a head actuator.
A conventional electrical lapping guide (ELG) type lapping apparatus which has been placed on the market is provided with a lapping jig of the swinging type, which is placed on a lapping plate of the main unit of the apparatus and is adapted to be able to move from the inner circumferential portion of the lapping plate to the outer perimetric portion thereof. The bar is mounted on the bottom surface of this lapping plate. Slurry, which includes lapping powder composed of an industrial diamond abrasive, is supplied from a slurry supply unit onto the rotating lapping plate. The bar is lapped by swinging the lapping jig under such conditions.
Such a lapping jig is provided with a correction mechanism, for compensating for the lapping amount along the bar, such as, for example, a mechanism of pushing both end portions and the central portion of the bar. Accordingly, if the bar to be lapped has a warp or inclination against the rotating lapping plate, the warp or the inclination is corrected to be flat against the lapping plate by freely changing the push-out (or extruded) amounts corresponding to the lateral sides and the central portion of the bar. This correction mechanism is connected to a control unit which uses a computer and is adapted to operate in accordance with a correction signal sent from the control unit. Further, a piezoelectric device element may be placed in a transfer jig (namely, a workpiece mounting member) in which a bar is mounted, and moreover, the jig may be provided with a mechanism for correcting the warp of a bar by applying the voltage to this piezoelectric device from the control unit.
However, in the case that a bar of MR heads is lapped by the conventional lapping apparatus having a swinging mechanism, there occur the following problems: